Messages in this thread Patch in this message | | | Date | Fri, 22 Jul 2022 10:33:47 +0100 | From | Paul Cercueil <> | Subject | Re: [PATCH 4/4] iio: afe/rescale: Implement write_raw |
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Hi Peter,
Le ven., juil. 22 2022 at 00:16:36 +0200, Peter Rosin <peda@axentia.se> a écrit : > Hi! > > 2022-07-21 at 21:15, Paul Cercueil wrote: >> Implement write_raw by converting the value if writing the scale, or >> just calling the managed channel driver's write_raw otherwise. >> >> Signed-off-by: Paul Cercueil <paul@crapouillou.net> >> --- >> drivers/iio/afe/iio-rescale.c | 22 ++++++++++++++++++++++ >> 1 file changed, 22 insertions(+) >> >> diff --git a/drivers/iio/afe/iio-rescale.c >> b/drivers/iio/afe/iio-rescale.c >> index 5c9970b93384..0edb62ee4508 100644 >> --- a/drivers/iio/afe/iio-rescale.c >> +++ b/drivers/iio/afe/iio-rescale.c >> @@ -141,6 +141,27 @@ int rescale_process_offset(struct rescale >> *rescale, int scale_type, >> } >> } >> >> +static int rescale_write_raw(struct iio_dev *indio_dev, >> + struct iio_chan_spec const *chan, >> + int val, int val2, long mask) >> +{ >> + struct rescale *rescale = iio_priv(indio_dev); >> + unsigned long long tmp; >> + >> + switch (mask) { >> + case IIO_CHAN_INFO_SCALE: >> + tmp = val * 1000000000LL; >> + do_div(tmp, rescale->numerator); >> + tmp *= rescale->denominator; >> + do_div(tmp, 1000000000LL); > > do_div is for unsigned operands. Can val never ever be negative? > What about the numerator and denominator, can those be negative? I > think this code should live in a new rescale_process_inverse_scale > function, or something like that (and a few tests could be added to > drivers/iio/test/iio-test-rescale.c)
I can do that.
> >> + return iio_write_channel_attribute(rescale->source, tmp, 0, >> + IIO_CHAN_INFO_SCALE); >> + default: > > What if the source driver has a .write_raw_get_fmt callback? That bit > of info is silently dropped (with no comment that a shortcut has been > taken). How does inverse rescaling mix with a .write_raw_get_fmt that > returns e.g. IIO_VAL_INT_PLUS_MICRO_DB anyway? I think all cases might > get a bit hairy to support, so I think you need to do some filtering > and somehow fail the .write_raw call if the .write_raw_get_fmt of the > source returns something that gets too difficult to support.
If the inverse rescale uses the same code as rescale_process_scale() then it becomes problematic, yes, as it likes to change the type of the value.
What I could try - compute the inverse of the value, then find the closest scale value+type that the source driver supports, and use this as the value+type. Then the only failure point would be if .write_raw_get_fmt returns something different than the formats returned by .read_avail, but that sounds unlikely to happen.
Cheers, -Paul >> + return iio_write_channel_attribute(rescale->source, >> + val, val2, mask); >> + } >> +} >> + >> static int rescale_read_raw(struct iio_dev *indio_dev, >> struct iio_chan_spec const *chan, >> int *val, int *val2, long mask) >> @@ -250,6 +271,7 @@ static int rescale_read_avail(struct iio_dev >> *indio_dev, >> } >> >> static const struct iio_info rescale_info = { >> + .write_raw = rescale_write_raw, >> .read_raw = rescale_read_raw, >> .read_avail = rescale_read_avail, >> };
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